Unleaded Gas and Reading Spark Plugs

What's the true story?
I read that our modern unleaded gas does not allow a "true" as compared to the past, spark plug insulator reading.
Something about the insulator color should stay white and as such is no longer a way to read for proper mixture.
From what I understand, one should have the bottom base ring showing a nice little buildup of black, but that true
jetting mixture is read way way down into the insulator with a light and magnifying glass.

My insulators have turned a medium brown throughout and I do have the slight black soot on the base ring.
This seems ok. When I start it takes a city block or so, that's all, to over come the initial leanness and hold an idle.
If I raise the needles just one notch, the motor runs noticeably stronger, but the insulators turn dark brown and the base rings gets loaded up. With this extra richness just to run a little stronger, deeper sound, am I adding unnecessary carbon build up to the chambers and pistons? Better to run a little leaner nowadays?
Just what is the correct way to read for unleaded gas in our motors?
Anyone able to show some good pictures of plugs that are correctly jetted?

The leaner burning ethanol and other additives for cleaner burning pretty much limits you to what you know and see and feel already. New fuels tend to burn leaner so general direction to tune today is richer, but not sooty coking. You can fudge in between needle positions by float level. New age tuning requires digital sensors and meters to track it. At least timing and heat range can still be read in plugs, thermal stain should be mid elctroke, just before bend in hook. If runs better but loads up with needle a groove up then might try a hotter range plug.

Amals ? Sounds like you have it pretty right to me. I like to run on the rich side if it's not detrimental, especially in Summer.
Try a shim (washer) under the clip, half the thickness of the distance between the grooves, to raise the needle a little.
And or a hotter plug... AC.